Dictionary

Definition

A dictionary in Python is a collection of key-value pairs where each key is unique. It allows for efficient data retrieval based on the keys.

5 Must Know Facts For Your Next Test

1. Dictionaries are mutable, meaning they can be changed after creation.
2. Keys in a dictionary must be immutable types like strings, numbers, or tuples.
3. Values in a dictionary can be of any type and can be duplicated.
4. Dictionaries are unordered collections prior to Python 3.7; from Python 3.7 onwards, they maintain insertion order.
5. Common operations include adding, deleting, and accessing items using their keys.

Review Questions

• What distinguishes a dictionary from other data structures like lists or sets?
• What types of objects can be used as keys in a Python dictionary?
• How does Python handle the order of elements in dictionaries starting from version 3.7?

Related terms

Key: An immutable object that uniquely identifies an entry in a dictionary.

Value: The data associated with a key in a dictionary.

Mutable: A property indicating that an object can be modified after its creation.